How Are the Reptiles Doing?

: Meiri: 40 to 43% of crocodiles and turtles are classified as threatened. Only 15% of lizards and 10% of snake species are. But the thing is, we know so little about them that we tend to assume they're doing okay. We've done some modeling with that, and we consistently find that probably a very large proportion of these data deficient species or species that were never classified by the IUCN, the vast majority of which are lizards and snakes, would probably be ranked as threatened if they were properly assessed.

00:00:36: Hahn: Welcome to Inside Biodiversity. This podcast is hosted by iDiv, the German Centre for Integrative Biodiversity Research. My name is Volker Hahn. I'm head of the Impact unit at iDiv. My guest today is Shai Meiri. Shai is a zoologist and a macro ecologist at Tel Aviv University and the University of Melbourne. He's best known for his research on global biodiversity patterns, particularly in reptiles. So he was the perfect guest to ask how are the reptiles doing? Here is my conversation with Shai. Why did you decide to study reptiles and not other species groups? Do you have a specific link to two reptiles where you chose them?

00:01:19: Meiri: I was when I was, I don't know, 11 or 12 years old, one of those kids who had run around and we lived in a village, and I tried to catch every reptile that I could get my hands on, but then I stopped. I was not one of those kids who, you know, raised vipers as pets or, uh, has a lifelong obsession. I liked animals in general. And I started studying zoology, and I did my PhD on mammals. Uh, but then for my postdoc, um, I had an opportunity to choose which taxon to work on, and I chose, uh, but as long as the question or the, the approach was what we call macro ecology. So basically gathering large sets of data. And I chose reptiles then for some scientific and some let's call it strategic reasons. The scientific ones was that macro ecology was hardly done on reptiles at this stage. So everything I would have chosen or I would have found would, would have been new. And so it proved to be. And also because birds and mammals were already well known, I knew that I'll have interesting things to compare what I find to. And then there was the issue of, oh, what will help me actually get this, uh, postdoc? It was at Imperial College. Everyone will go and talk about birds or mammals. I want to stand out. Right. I'll talk about reptiles. It looked like there would be potentially kind of good career opportunities with reptiles. And in Israel, which is where I came from and where I went back to, uh, after my postdoc, so. And then. And I always liked reptiles. Right. So I like reptiles, I like mammals, I like amphibians, I like birds. Uh, I knew I wouldn't I wanted to work on land vertebrates, but I could have chosen any group.

00:03:12: Hahn: Are there specific, uh, species amongst reptiles that you like best?

00:03:19: Meiri: Uh, there are many, um, among those that I still want to to find in the field. Uh, but I, I'm really aiming for, um, is, uh, the Australian lizard called Moloch or the thorny devil. That's just one of the coolest animals. Uh, around. There are fantastic big geckos, both in Madagascar and in northeastern Australia. Uh, that want to want you to think they're leaves. And they're doing very, very a good job of this, um, That I, that I like a lot. I like like the lizards in general, especially like the skinks and the, again, Australian legless lizards that we may be starting to work on here in a few months time. So but yeah, there are lots of reptiles that I like.

00:04:13: Hahn: Some of the species you mentioned. Usually people associate them with dry and arid habitats like reptiles live in the desert. And I guess that's true for some. But if you look at the overall picture, most reptiles actually live in forests. Can you explain that? Probably not a misconception, but. But that difference?

00:04:34: Meiri: There are two ways of looking at this. First, it's true that most reptiles live in tropical regions. The thing is, it's true for every group, large group of organisms anywhere in the world. And with reptiles, it's probably less pronounced than in the birds or in mammals, and certainly less pronounced than in amphibians. And you do find relatively more reptiles in deserts. Then you find mammals, birds, and especially amphibians. Again, amphibians need water. They don't work well in deserts. Uh, reptiles get around quite well in deserts, whereas most other groups find them very hostile. So, for example, you asked about my favorite reptiles, one of the species that I studied and still study a bit is this tiny little gecko found in the Sahara Arabian desert that I study in Israel. Tropiocolotes yomtovi tiny little things about 2.5cm from, uh, you know, from the snout to the cloaca to the opening of the digestive and reproductive system weighs, like 0.2 of a gram. Something like that. In adults, if you take them out of their shelter in the middle of the day and put them in your hand and expose them to the sun, they will die in just over a minute. I've seen it happen, unfortunately, in their natural habitat, but they thrive in deserts and other species do not stay there active at night, so it's easier for them, right? So if you look at the overall diversity of reptiles, it's higher in the tropics. If you look at which taxon is most prevalent in desert relative to what you'd expect, then it's reptiles for sure.

00:06:28: Hahn: So it's comparing it to other species groups that make them thrive in dry habitats.

00:06:36: Meiri: Yeah. Is there a physiology that that allows them to, on the one hand, lose very little water and to, um, make a living with very little food? And these two factors, uh, basically Prohibit most of the birds and mammals from inhabiting deserts. It's a food issue, and with amphibians, it's the, um, the dryness that gets them. And reptiles can do okay with little food and and high, uh, heat and aridity.

00:07:09: Hahn: In one of the previous episodes, we talked about biodiversity change with mammals. That was an episode with Carlo Rondinini. What was interesting is that he could name species and species groups that were declining, but also those that are increasing. Do you find the same for reptiles? Is it very heterogeneous, complex pattern of, uh species doing well and doing badly?

00:07:35: Meiri: It's less balanced, I would guess. I mean, I don't know the numbers for mammals, but if you look at the number of species for which the IUCN International Union for Conservation of Nature, uh, that assesses, uh, population declines or increases. Um.

00:07:54: Hahn: That's the so-called red list, right?

00:07:57: Meiri: Yes, that's the red list. The largest group of reptiles, 40% of species have have a status unknown. I would assume that this is higher than in mammals, certainly higher than in birds. I don't know exactly what that would be. My first guess of this, the of the rest is actually 40% unknown and 20% no one looked at. Right? So 60% basically no idea. 30% is 29%. I have to be more precise. Are classified as stable. 11% are decreasing and only 0.4% are increasing. So 52 species out of uh, over 12,600 species nowadays are increasing. And they are usually those associated with humans or species that we're doing so badly and and we're lucky enough. And in reptiles, it's not immediately obvious that there will be some, um, conservation effort directed to them. Some crocodiles, some New Zealand lizard. Lizards. Sorry, some iguanas in the Caribbean. They're kind of the most prominent of these groups that are increasing. But overall, 52 species increasing and 1424 are classified as decreasing. Right? And then again, for the vast majority of species, over 8600 species, we just don't know.

00:09:34: Hahn: What.

00:09:34: Meiri: Even that you know, of these 52 species. There's one species that I don't understand, right? There's a venomous snake from western Africa, as far as I know. As far as I know, it's only known to science from one specimen collected in 1957. The IUCN says it's increasing. Uh, it probably increases slowly.

00:09:58: Hahn: It seems like there's a lot less data and knowledge about how reptiles are doing and why. Why is why is that? Why do we know so much less about reptiles compared to birds or compared to, um, to mammals? Maybe to amphibians, I don't know. Why are reptiles? Have they been overlooked? Or don't we care?

00:10:20: Meiri: In reptiles, the general public either doesn't care or think they are pretty bad. And yeah, let's. Let's kill the vermin. Uh, when.

00:10:33: Hahn: You think of snakes.

00:10:34: Meiri: With.

00:10:35: Hahn: Probably.

00:10:36: Meiri: Yes, mostly, but but many people would not make the distinction, you know. And, you know, I've been pointed out by some locals and some places that I will not name now said, oh, there's a very highly venomous snake here and turned out to be a skink. Very nice skink. So many people just I'm not going to bother to count legs. Right. If it's a reptile, it's bad enough for me. And if it's a snake, I don't know. I will assume it's. It's deadly and I will kill it. Uh, for example, we, uh, described the snake. Tiny little thing, five grams. No more from the Negev desert in Israel. Uh, about ten years ago, one of the something like seven known specimens of this snake was brought to us by a woman who found it near her home and got so afraid it was a juvenile that she just picked up a book and smashed it to death. It was a two gram animal, maybe ten centimeters in length, completely harmless. But she saw a snake. She panicked. Um, so bang. And unfortunately, that's a common reaction. Now, there are very few reptiles that that we get the gut feeling that we get towards maybe pandas on the one hand or tigers on the other. Or dolphins to be exact. There are seven. All of them are marine turtles. The marine turtles are a very, very well known, very well studied worldwide. They have huge distributions. Mostly it's kind of difficult to say whether they are actually threatened or not. And there are various issues, but they receive lots and lots of effort, lots and lots of budget, and everybody likes them. So I have a turtle envy, right? I envy these marine turtles, uh, dealing with, uh, with squamates, with birds.

00:12:20: Hahn: And what would you say really makes sense when I think of the public and people who don't know much about biology, but those that collect the data are also biologists. Do they also have these this bias or how or does it translate from.

00:12:39: Meiri: Yes or no birds? There are more people interested in and loving birds worldwide than probably all animal other animal groups put together. If you look at the Global Biodiversity Information Facility Gbif that collects data on all organisms worldwide, from citizen science, from museums, etc., 70% of their data are birds because they're easy to see, people like them, people go out of their way to look for them. The same goes with mammals, but the numbers are orders of magnitude less. Right. Sorry. Same with reptiles. Probably said mammals. And that's on the one hand. On the other hand, there are very, very seldom perceived as cute or adorable the way some large mammals, big cats, elephants, pandas, etc. are. So if you look at the dedicated project to reptile conservation at a species level, I'm not saying let's protect the habitat. But even if you protect the habitat, it is the habitat of of the panda or something like that. There will be orders of magnitude fewer such projects dedicated towards reptiles than there would be towards mammals or birds amphibians. I think it's probably similar to to reptiles. I don't have data, but that will be my feeling.

00:14:02: Hahn: So really, our feelings about these animals translates into what we monitor our knowledge about them, but also conservation, as you mentioned.

00:14:11: Meiri: 100%. And again, if you look at the invertebrates, the situation is even worse, right? There are a lot of people who love who love reptiles. Probably fewer love earthworms or slugs.

00:14:25: Hahn: Yeah, true. And then it makes a difference whether it's a mosquito or a dragonfly, of course. Or a butterfly. Okay.

00:14:35: Meiri: Um, a venomous snake versus a, you know, just your old lizard. Uh, we did look at one point at the public interest in reptiles, as evident from Wikipedia pages, views. And the highest ranking species were either very, very large or could kill you. Or both.

00:14:56: Hahn: Are there specific reptiles or reptile groups that are doing worse than others, or are they all the same? I mean, you mentioned that maybe turtles are doing better because we care more for them with our conservation measures.

00:15:11: Meiri: So no, turtles are actually doing worse. Uh, turtles and crocodiles have over 40% of the species threatened with extinctions, according to the IUCN. But I think the gap is unfortunately lower than than the numbers would suggest, because turtles are just so much better known. So we know they're doing poorly With a lizard or a snake. And again, something like 40 to 43% of of crocodiles and turtles are classified as threatened. Only 15% of lizards and 10% of snake species are. But the the thing is, we know so little about them that we tend to assume they're doing okay, because the IUCN is very conservative when it comes to defining species of threatened. They need good, hard evidence. If they don't have good hard evidence, they classify it as least concern or data deficient. We've done some modeling of that, and we consistently find that probably a very large proportion of these data deficient species or species that were never classified by the IUCN, the vast majority of which are lizards and snakes, would probably be ranked as threatened if they were properly assessed. If we had the data about them. What we have is proxies, what the proxies suggest that they would be threatened.

00:16:39: Hahn: I saw these papers of yours, and I found that quite interesting for me. It was surprising because I would have guessed that the IUCN would actually focus on those species that you expect are threatened, but apparently it's more the other way around that the ones that we don't monitor closely might actually be more threatened on average, than than the ones that are monitored.

00:17:04: Meiri: Yeah. And we have a very large number of species that we know so little about that we classify them as data deficient or they were never assessed often because they are new. So they are new to science. And so these do not get the threatened tag right. They get the data deficient or then never noticed that which we call unclassifiable. You can't say whether they're threatened or not. And together this amount to 30% of lizard species, 33% of snake species. So we are talking about thousands of species here to just to to make it clear, there are fewer than 400 turtle species recognized worldwide. There are well over 12,000 lizards in snake species. Right. So it's over. It's something like 97% of the species are of reptiles are snakes and lizards.

00:18:03: Hahn: In preparation for this interview, I didn't find much about the common biodiversity metrics like how our population changing, how this local species richness, changing abundance, biomass. But most of what I found was this categorization of extinction risk according to to the red list, are those metrics, let's say abundance change, population change. Are they just so scars. And if that's the case, what does the IUCN base its assessment on? How threatened a species is.

00:18:44: Meiri: Okay, that's an interesting question. And again it differs very, very sharply between, uh, turtles and uh crocodilians on the one hand and lizards and snakes on the other hand. All of these are based on population sizes, right? So not on biomass or species richness, which would probably hardly change in most places except, you know, very localized, uh, places that were, uh, heavily modified by humans. The IUCN, to determine that the species is threatened goes to basically either saying it has a very, very small population or the population is decreasing with turtles and, um, and crocodiles, we can know often, especially for the species that are not very wide ranging or the population size is, and often whether the population is actually decreasing or increasing. We can do it with pandas, we can do it with tigers. We can actually count them. We can count elephants. We can't count snakes. Okay. Very, very difficult to get actual abundance data on snakes or lizards. Much easier with turtles or crocs. Crocs. You have to look in or near. Reporter. It narrows it down. Most turtles are also freshwater. They are bigger. They're more conspicuous with squamates. Very, very difficult. So we don't get the population data. And if you.

00:20:15: Hahn: Share, can you briefly say what squamates. What does that include?

00:20:19: Meiri: Yes. Squamates are birds. Sorry. Yeah. Squamates are lizards and snakes. Okay, okay. And this is like. Lizards and snakes. Yes, yes. Sorry. So we can actually test whether the population has decreased or increased or remains stable. And we can also say how much it decreased or increased because to say a species is threatened, it needs to go above some threshold of decrease. Unfortunately, with turtles and crocs, we know that the increases is surpasses thresholds in about 40% of these cases. So when we say a turtle is threatened or a croc is threatened, it means we know the population has declined by, I don't know, 33% over ten years. Okay. Or or three generations, which is very long in these animals. In snakes and lizards, we don't know that because we don't have the population size data. So the what we do is we use another way that the IUCN can do it is go by what they call criterion B, which is basically saying they are localized. They have a small range geographically. If they have a small range and their population is declining, we can infer the decline. Okay. We don't actually have to have data, but we can say, but you know, the habitat is deteriorating or, you know, the habitat is being modified or there's an introduced species or climate change is hitting it. We don't have to put an actual number. We just say, if the, you know, if the geographic area started small and there is an inferred decrease in the population because of one of those processes or another, and there are some fluctuations or all sorts of other sub clauses, we can define a species as threatened. That's much more difficult than it sounds. And it, uh, it also means that we are basically being much more conservative when saying they have decreased because we don't know anything about the population. Again, you can also apply these criteria for turtles, but you don't see it. Why? Because we have better data that says that the population is declining. We don't even need the other criteria we already know. Again, there are also different threats, right? Crocodiles are prosecuted. Turtles are being hunted for the pet trade or for food. It also happens with with lizards and snakes, but potentially at least for food, for to a lesser extent, I think, because they are basically assessed as threatened in different ways that yes, I would have guessed the turtles and Crocs are in general more threatened, but uh, but the ratio is not two or 3 to 1 that current numbers suggest.

00:23:17: Hahn: Apparently there's high uncertainty data gaps. I understand that, and knowing how populations change, I assume, is also important To know which are the most important drivers for reptile change or declines in most cases. What do we know about the drivers?

00:23:39: Meiri: I want to distinguish between two two time periods. Basically, if you ask about extinct reptile species, then it's data or unequivocal. It's invasive species. Extinct species of of reptiles went extinct on islands mostly, I would say, during the 1890s, early 20th century. So this was an island pattern caused either by hunting or much more commonly because of invasive species. It still carries on to to today, potentially a bit more slowly. What we see now is extinctions being driven more by habitat loss. I think, by the way, this is not specific to reptiles. This pattern of island extinction during the 18th 19th centuries, potentially early 20th century is also found. We looked at this in in birds and other people have looked at this in mammals. It would be probably different for amphibians. Amphibians are a whole different kettle of fish or kettle of frogs. But if you look at threat, then the other thing quantifies that I think the degree of certainty, and that is quite low. I don't remember the data at the top of my head, but I think it's mostly habitat loss. Also invasive species, the pet trade, which is very big in some cases, some groups, uh, what we see increasingly, or at least we anticipate to see increasingly, is climate change.

00:25:19: Hahn: So what are the solutions? What are the most effective conservation measures, or is that too diverse? Because. Because the drivers are so different.

00:25:29: Meiri: Yeah. Well, if you ask me. The the best solution to nature conservation is to make sure that the human population doesn't grow as fast as it did during the 20th century, uh, maybe even 19th and 20th century. You know, I think families with six, seven, eight kids are not viable in the long run. Uh, not for, uh, nature, not for humankind, potentially, but we do. So we do see this.

00:26:00: Hahn: By 2100, we'll have like 10 or 11 billion people, and then it will slowly decline again.

00:26:06: Meiri: So yes. And I think even projections are potentially for saying that, uh, or current data are actually showing, uh, faster declines than these population models, uh, predicted. But, but that's, that's kind of the root of the problem. What's the solution to climate change? You know, nobody really knows what the solution to climate change is. It's probably a requires much more effort than is currently being done, either at the individual or the governmental level or organizational level. The solution to trade, I think, is better monitoring, better data, better policing, probably similar things, better biosecurity laws, etc. with regard to invasive species, habitat loss. Again, you know, more people, more food. But we need to I think the basically more nature reserves, larger nature reserves, better connectivity, putting nature reserves in places that are today devoid of them and maybe putting them strategically where we see that species are threatened or potentially going to be threatened in the future, could be a solution. There are all sorts of international agreements that that go with this. Right. But the implementation on the ground lags behind the nice words that politicians utter, unfortunately. But that's the right direction, right? And again, I think we can also do conservation more wisely if we go from the head and not from the gut. Many people may hate me for saying this. And again, I did say that, uh, that I envy the fantastic conservation success stories associated with, uh, with sea turtles. But they receive way, way, way, way more than their fair share of attention. We need to be very strategic. We need to go to the most needy species first, which means a we need to know who they are better. We need to prioritize our assessments better. We need to potentially come up with better ways to assess a population decline and current and future threats, and then we need to implement conservation efforts more widely and again, not go simply for the biggest, fluffiest, cutest species.

00:28:41: Hahn: Is there anything that an individual can do? What can I do and what can the listeners do to help reptiles specifically? Or is it the same as for biodiversity in general, which is also quite broad field?

00:28:58: Meiri: I don't think there is anything that is specific to reptiles, except for the fact that I think we need to understand that reptiles and even snakes are not necessarily bad. Even venomous snakes. Here in Australia we have some of the deadliest snakes worldwide, and many of them live with people in cities. And you don't hear about it. You don't hear about it because snakes don't go after you. You're not a potential food, and you're only a potential threat if you act unwisely. Basically, sticking your hands into places they shouldn't be, or provoking a snake or whatever. Best way, best thing is to let them go. If you look at whether they are actually good for humans or not, probably on the whole they're good except for some areas of the world, mostly in Africa and southern Asia where envenomation is is very, very frequent. It is a problem. It's a real problem. Many people world over. Die from snakebite again, especially in these areas. The snakes are doing worse. More snakes die of human aggression. But. But still, where it is a problem, there are ways to handle it. Even simple measures such as proper footwear. And it's not really even protective gear, just sturdy boots would do otherwise at the individual level. Just don't create reptiles automatically. Bad things. They don't deserve it.

00:30:33: Hahn: Shai last question very briefly. What would you like the audience to remember from this conversation? What's the most important for you?

00:30:44: Meiri: I think the audience should remember that that reptiles are fascinating. They are, to a large extent not harmful. They can be very interesting. They can be beneficial to humans, and they deserve both their respect and our efforts to conserve them after we've done them so much harm.

00:31:07: Hahn: Thank you very much, Shai, for this great conversation. If you enjoyed this episode, be sure to subscribe! Inside biodiversity is available on all major streaming platforms.